Circuit/System Description

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The heated oxygen sensor (HO2S) compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream, a fuel mass observer function is used to adapt a correction quantity using the difference between the measured and modeled oxygen content of the exhaust gas. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by an ignition voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the ECM. The ECM uses pulse-width modulation (PWM) to control the HO2S heater operation to maintain a specific HO2S operating temperature range.